Abstract: In order also to allow the detection, for example, of condensation of the inner side of an interface (window) using motor-vehicle rain sensors that exploit the interference, at a window wetted with moisture, with total reflection of light irradiated by a transmitter, several sensors are proposed that are sufficiently variable in terms of configuration and function that they contain, without complex adaptation actions, an implementable possibility for selectable inside/outside detection simultaneously with good discrimination between outside and inside wetting.

Abstract: In an optical sensor for detecting moisture on a windshield of a motor vehicle, in which the light radiation is deflectable to a detection area on the windshield situated in the light path between transmitter and receiver, the transmitter and/or the receiver have a transparent design and are integrated into the windshield. The transparent optical elements may thus be situated in the area of a wiped field of the windshield cleaned by the windshield wiper.

Abstract: The invention relates to a rain sensor, especially for a motor vehicle, said sensor comprising an optical waveguide (22) which can be arranged in a windscreen. According to the invention, the planar holographic coupling elements for coupling and decoupling radiation (4) are formed from layered photo-polymer parts (3) into which volume holograms are integrated. The photo-polymer parts (3) are arranged between the core (1) of the waveguide and the envelope of the waveguide (2), resulting in a simple production method and an increased flexibility in terms of the arrangement of the waveguide (22) in the windscreen.